Fluorous biphasic catalysis methods have been described in the art. A review of fluorous phase separation techniques in catalysis is described in de Wolf et al., Chem. Soc. Rev. 28(1): 37-41(1999); Hope and Stuart, J. Fluorine Chem., 100(1-2): 75-83 (1999); Fish, R. H., Chem. Eur. J, 5:1677-1680 (1999); and Barthel-Rosa and Gladysz, Coord. Chem. Rev., 192: 587-605 (1999). Fluorous biphasic catalysis is a method of homogeneous catalysis that allows the catalyst and the products to be separated after the reaction. In this scheme, shown in FIG. 1, a highly fluorinated catalyst is dissolved in a highly fluorinated solvent (the fluorous solvent) and organic reagents are dissolved in a traditional organic liquid. The two liquid solutions are placed together, and the reaction takes place, often requiring heating and stirring. After the reaction, the organic products are removed by pipetting off the organic liquid solution. The catalyst remains in the fluorous liquid. Unfortunately, the fluorous solvents used as the lower liquid phase are usually volatile, environmentally damaging and expensive to replace. An example of fluorous biphasic catalysis is the fluorous biphase hydroformylation of olefins as described in Horváth and Rabai (1994), Science 266(5182): 72-75.
Supercritical antisolvent precipitation, in which a solid compound is dissolved in an organic solvent and then made to precipitate as a fine powder by the rapid addition of carbon dioxide gas, has been described in Reverchon, E., J. Supercrit. Fluids, 15: 1-21 (1999); Bertucco, A., “Precipitation and crystallization techniques” in Chemical Synthesis using Supercritical Fluids; Jessop and Leitner, Eds.; Wiley-VCH: Weinheim, 1999, pp 108-126; and Field et al. J. Am. Chem. Soc., 122, 2480-2488 (2000). The article by Field also described a somewhat slower addition of carbon dioxide gas in order to obtain very small crystals of the solid compound.
Methods of synthesis and separation in which organic/fluorous phase separation techniques are used to effect separations, and compositions of matter comprising fluorous Si, Sn and Ge compounds are described in U.S. Pat. Nos. 6,156,896; 6,376,676; 6,372,906; 5,777,121; and 5,859,247.
Crystallizing under gas pressure, in which an organic compound is made to melt by the addition of carbon dioxide pressure and then is made to crystallize by the slow release of the carbon dioxide, is described in Freund and Steiner, Crystallization under Gas Pressure” in High Pressure Engineering, von Rohr and Trepp, Eds., Elsevier Science B. V. (1996). This technique is limited to those few compounds which can be made to melt by carbon dioxide pressure at moderate temperatures. The growth of crystals from supercritical carbon dioxide or related fluids is described in U.S. Pat. No. 4,512,846; Tai and Cheng, AIChE Journal, 41:2227-2236 (1995). In this technique, an organic compound such as naphthalene is dissolved in supercritical carbon dioxide and then made to crystallize by slow release of the carbon dioxide pressure. The observation that highly fluorinated metal complexes have good solubility in supercritical carbon dioxide was described in Laintz et al., J. Supercritical Fluids, 4:194-198 (1991). The observation that highly fluorinated surfactants have good solubility in carbon dioxide is described in Consani, K. A. and Smith, R. D., J. Supercrit. Fluids, 1990, 3: 51-65 (1990). Polymerization of styrene in solutions with compressed carbon dioxide as antisolvent is described in Liu et al., J. Supercritical Fluids, 20:171-176 (2001).
Fluorous solvents are disadvantageous because of their long lifetime in the environment, high cost, and contribution to the greenhouse effect. It would be advantageous if the use of fluorous solvents could be avoided in solvation, recrystallization and catalytic reaction techniques using fluorinated compounds.